PRTN3 and rheumatoid arthritis: A retrospective, cross-sectional comparative study on 20 cancer patients with de novo IA of the peripheral joints after the initiation of ICI therapy (ipilimumab, nivolumab, pembrolizumab, or combination) found that IA-irAE resembled autoantibody-negative RA in certain immunological characteristics, including negativity for RF and ACPA and a speckled pattern of anti-nuclear antibodies [97].